1. Field of the Invention
The present invention relates to a medical breast-image capturing apparatus which acquires a medical image of a breast of a test subject using radiation such as X-rays, ultrasonic waves, MRI, etc.
2. Description of the Related Art
An improved X-ray mammography apparatus capable of photographing a breast of a patient (test subject) while the patient is in a prone position is discussed in, for example, Japanese Patent No. 2691073.
In the mammography apparatus described in Japanese Patent No. 2691073, photographing is carried out while the patient lies on a bed in a prone position. The bed functions as a support platform and is provided with a breast-receiving aperture through which the patient inserts a breast. The breast that hangs down is exposed to X-rays while it is pressed between compression plates. In this apparatus, the patient is not required to be in an unnatural position and can relax during the procedure, so that accurate measurement can be performed while suppressing the patient's movement during the photographing process.
However, similar to the known mammography technique, it is necessary to press the patient's breast with the compression plates in the above-described structure. This can give considerable pain to the patient. Therefore, many patients have a negative impression about mammography that the procedure involves pain.
In the above-described apparatus, an area that can be photographed in a single process is limited because of the shape of the photographing subject. Therefore, a plurality of photographing processes must be performed for each breast, and the above-mentioned process of pressing the breast must be performed each time. In addition, since information obtained by the photographing process is two-dimensional data, photographing must be performed in a plurality of directions to determine X, Y, and Z coordinates of a lesion necessary for guiding a biopsy needle.
In the above-described apparatus, photographing is performed while the patient is in a prone position and the patient's breast hangs down. In general, when a breast is divided into four quadrants, breast cancer is often found in an upper outer area, that is, in an upper area near the shoulder. Therefore, the photographing area is required to cover this area. In the known mammography method in which photographing is performed while a patient is in an upright position, an image of deep tissue in the upper outer area of the breast can be obtained by photographing this area in a medical lateral oblique direction.
However, when a breast that is inserted through a substantially circular aperture is photographed, it is relatively difficult to pull out the upper outer portion of the breast compared to an outer lower portion thereof. In addition, when the breast inserted through the aperture is pressed between the compression plates while the patient is in a prone position as described in Japanese Patent No. 2691073, rear breast tissue can be pushed away from the X-ray irradiation area by the edges of the compression plates.
In the above-described known apparatus, the breast-receiving aperture is substantially circular and has a fixed size and shape. However, patients have different body sizes. Therefore, it is difficult to set a necessary photographing area for each patient using the hole with a fixed size and shape. As a result, there is a risk that the area of a portion presented in the photographing area will vary.